The present invention relates to video decoders, and more particularly to a decoder using an adaptive non-separable digital filter for more accurate decoding of diagonal features.
Existing video decoders adaptively select between comb and notch filters. The notch filter is selected when the horizontal correlation is greater than the vertical correlation. On the other hand the comb filter is selected when the vertical correlation is greater than the horizontal correlation. These filters give excellent results when the image represented by the video signal is horizontally or vertically correlated, but they lose precision as the correlation deviates from the horizontal or vertical. Composite video input signals may be correlated in any direction. Thus for images that are correlated at a diagonal, false color values may be introduced into the decoded video signal and luminance details may be blurred.
What is desired is a decoder that is adaptive to provide excellent results regardless of the angle of correlation of the video signal.